hemostatis within blood and hematology Flashcards
what makes up the cardiovascular system?
heart, blood vessels, and blood
what is hemostatsis? when does it occur? what is it triggered by?
stoppage of bleeding
occurs in responce to blood vessel damage
triggered by chemicals released or activated by damaged cells and platelets
what is the function of hemostasis?
functions to prevent blood loss and build a framework for tissue repair
what are the three phases within hemostasis?
vascular phase
platelet phase
coagulation phase
what is the vascular phase?
a vascular spasm of damaged vessels which causes constriction
smooth muscle contracts to reduce blood flow
what do the endothelial cells lining the blood cells release in the vascular phase?
endothelial cells release endothelians which are peptide hormones
what do the endothelins stimulate/make?
stimulate contraction of smooth muscle in blood vessel wall
stimulate division and repair
make endothelium sticky
what is the platelet phase?
platelets adhere to collagen fibres which are exposed when endothelium are damaged
platelets aggregate as platelets become sticky
results in formation of a platelet plug
what does platelet adhesion/aggregation activate?
the platelet
what do activated platelets release?
chemicals and granules which contain many substances
what substances do the granules contain?
serotonin - stimulates vascular spasm
thromboxane- stimulates platelet aggregation
PDGF- platelet derived growth factor, promotes vessel repair
Ca++ - promotes coagulation
how is platelet aggregation an example of positive feedback?
as more platelets aggregate, more chemicals are released, attracting more platelets.
what is coagulation?
blood clotting or blood goes from liquid to gel
what does the coagulation phase result in?
formation of a clot
what is a clot?
a tangle of fibrin (fibrous proteins) and cell
what triggers clot formation?
triggered by sequential activation of clotting factors
how do clotting factors circulate in what form?
circulate as inactive procoagulants and must be activated for coagulation to occur
how are clotting factors numbered?
I thought XIII in order of discovery
where are most clotting factors made?
made in the liver
steps in coagulation?
- vascular spasm
(smooth muscle in blood vessel wall contracts) - platelet plug form
(platelets stick to collagen in exposed vessel wall and platelets stick to each other - activation of platelet
(platelets are activated by collagen and by chemicals released by aggregating platelets and by chemicals released by damaged cells) - coagulation
(a cascade of activation of clotting factors in the blood causes a network of fibrin to form, trapping proteins and cells = clot)
what is the intrinsic pathway ?
initiated within blood
what triggers the intrinsic pathway?
triggered when clotting factors XII and platelets are activated by collagen
what does the intrinsic pathway require?
requires platelet phospholipid which is expressed when platelets exposed to collagen( collagen is a c.t and walls of torn blood vessels)
when can the intrinsic pathway occur?
can occur when blood is exposed to glass, a negatively charged surface which has the same effect as collagen (eg blood in a test tube)
how long does the intrinsic pathway take?
slow about 2-3 min
what is the extrinsic pathway initiated by?
intitiated by chemicals external to the blood
how is the extrinsic pathway activated?
activated by a chemical released by damaged cells
what do damaged cells release?
they release TF which is tissue factor/thromboplastin which activates platelets
how long does the extrinsic pathway take?
faster under 2 minutes
what does both pathways activate?
both activate clotting factor X which initiate the common pathway which results in network of fibrin
